Facebook Design - Devices - Images and Sketch files of popular devices.
Sketch Extensions - An official collection of Sketch extensions & plugins
Device Shots - Generate high-resolution device mockups using a screenshot.
Framer Inventory 3 for Sketch - Import states & export prototypes from Sketch to Framer
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Remake - A way to make web apps with just HTML & CSS